Hybrid inflators for vehicle occupant restraint systems utilize a combination of stored inert gas and the products of combustion of pyrotechnic material to deploy an airbag. The inert gas is stored in a chamber at a relatively high pressure on the order of 2,000 to 4,000 pounds per square inch. The pressure chamber is adjacent to a combustion chamber that contains an initiator and a pyrotechnic material for producing hot combustion gasses which are delivered to the stored inert gas. The mixture of the hot combustion gasses and stored inert gasses are delivered through an outlet to inflate the airbag of the occupant restraint system.
Hybrid inflators are particularly useful in that no Azide is required in the inflation system, and that complex filters are not required to cool and clean the gasses.
The housings of hybrid inflators are generally fabricated of machined and/or forged metal parts and numerous configurations are provided in the art for delivering the hot combustion gasses of the pyrotechnic material to the gas storage chamber, and for opening an outlet passage of the housing for inflating the airbag. Examples of such structures are shown in Vancil U.S. Pat. No. 3,788,667, Grosch et al. U.S. Pat. No. 3,797,853, Grosch et al. U.S. Pat. No. 3,836,170, Merrell U.S. Pat. No. 3,856,180, Merrell U.S. Pat. No. 3,856,181, Johnson U.S. Pat. No. 3,868,124, Merrell U.S. Pat. No. 3,869,143, Zeigler U.S. Pat. No. 3,865,273, Smith et al. U.S. Pat. No. 3,944,249, Meacham U.S. Pat. No. 3,948,540, Goetz U.S. Pat. No. 3,960,390, Marlow U.S. Pat. No. 3,966,225, Roth U.S. Pat. No. 3,966,226, Hay U.S. Pat. No. 3,968,980, Woods et al. U.S. Pat. No. 5,076,607 and Frantom U.S. Pat. No. 5,199,740.
Because the inflators in the foregoing patents, and particularly the ones which are toroidal in configuration, comprise machined and/or forged parts, they are accordingly complex in the number of parts and assembly, and high in cost. Given the widespread use of inflators, there is a corresponding need to reduce the complexity and cost thereof, as well as the size and weight without sacrificing efficient operation and reliability.